This invention relates to a high pressure rotary valve suited for use in the conveying or feeding of flowable, or pelletized granulated bulk material, friable products, fine powders, and the like. A pneumatic system of positive blowers and negative pressure means is normally used for imparting the conveying forces needed for moving the material to and from the valve outlet through the system.
Valves of the type contemplated include a housing defining a chamber and having a top inlet and a bottom outlet communicating with the chamber. Within the housing chamber there is provided a rotor which includes a plurality of blades supported on a horizontal shaft. The material being conveyed is fed to the housing inlet and then into the spaces defined between the blades. The rotor movement conveys the material to the outlet location of the housing for discharge of the material from the housing. Since the rotor speed can be controlled, the valve serves as a means for regulating the rate at which the material is conveyed in the feed line extending from the housing outlet to the equipment being supplied with the material.
It is important to provide means for sealing of the housing chamber so that the material being conveyed does not penetrate into regions where there are relatively movable parts, such as the area occupied by the rotor shaft which moves relative to bearings mounted in the housing. Such penetration, particularly in the case where relatively abrasive materials are being handled, can cause undue wear of parts and excessive downtime for replacement thereof.
Critical to efficient and consistent material flow through the pneumatic system, as well as maintaining material integrity, is the sustaining of line gas flows. Rotor, housing and bearing arrangement and assembly methodology are critical to prevent loss of mass and volumetric gas flow. When left unchecked, such drops in gas flow adversely effect material conveyance throughout the system.
The use of seals is also important for purposes of preventing leaking of the material being conveyed into the atmosphere surrounding the housing. This is particularly the case where toxic materials or the like are being conveyed.
The provision of adequate sealing arrangements is often problematical due the fact that the material is being conveyed under high pressure conditions, thereby increasing the tendency for movement of the material axially with respect to the rotor shaft rather than towards the discharge end of the housing. Packing glands and O-ring arrangements have been designed with a view toward eliminating or minimizing such problems, however, such prior art arrangements have been proven to be either unduly expensive, have been subject to frequent maintenance, have been ineffective, or have been characterized by a combination of these problems.